Look Inside BMW's Ultra-Green i3 Factory

PopMech takes a tour of the German production facility where BMW builds (what it hopes to be) the car of the future.

PopMech takes a tour of the German production facility where BMW builds (what it hopes to be) the car of the future.

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Look Inside BMW's Ultra-Green i3 Factory

BMW claims its i3 electric vehicle, which debuts at the end of the year, is the world's most sustainable car. That big boast hinges on another claim: that the wind-powered, carbon-neutral production plant near Leipzig, Germany, is the world's most sustainable car factory.

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The i3 is BMW's first mass-market electric vehicle, something they've been teasing repeatedly at recent auto shows. While the company dipped a toe in the EV pool with electric versions of the 1-series and Mini coupe, few made it into the hands of owners. Plus, those cars were conversions of existing architecture. The i3 takes advantage of a design custom-made for its motors and batteries, and also uses more composite materials in its construction (and in greater volume) than any previous BMW. And if that weren't enough, the company promises the i3 will stay true to the brand's "Ultimate Driving Machine" motto.

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The i3's 507-pound, 22-kilowatt-hour square battery pack sits under the floor and is cooled by both ambient air and the air conditioning. It consists of 96 Samsung-made cells, but the installation, the aluminum-alloy case, and the control electronics and software are BMW's design. The cells have a squared-off shape to aid packaging and cooling. "[They're] about the size of a Tom Clancy novel," says Patrick Müller, the project leader for powertrain.

The key to the battery pack's 10-year warranty is maintaining its temperature between minus 5 and 37 degrees Centigrade (23 to 99 degrees Fahrenheit). The 168-hp BMW-designed AC motor gives 0-to-62-mph acceleration in 7.9 seconds, and top speed will be limited to 93 mph. Range is quoted at 140 miles in the EV Combined cycle, but is more realistically between 80 and 100 miles, which is about 30 percent more than the Nissan Leaf's. The i3 is expected to be priced at about $40,000 when it finally comes out at the end of the year.

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BMW says that more than half the sales of the new i3 worldwide, and most units sold in the U.S., will be of a range-extender version, with a 65-cc, parallel-twin-cylinder motorcycle engine. The range extender will double the battery-only official range claim of 140 miles.

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Carbon fiber is the key to giving the i3 its low curb weight (for an EV) of 2755 pounds. But the material is typically reserved for low-volume, expensive cars—consider the carbon-fiber roof on the current range of BMW M cars, which BMW has been making for over a decade. That process is industrialized (you can see it done on YouTube), but it's slow and drawn out. In fact, the slow production cycle time was the main problem BMW faced when planning i3 production.

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"The key to reaching our targets for range and performance, as well as having a fast, exciting vehicle that is fun to drive, is to get low weight, because we had to compensate for the battery," says Carsten Breitfeld, head of the i project. "So the question wasn't whether to use carbon fiber or not, but how to optimize production. We are going into territory where no car manufacturer has ever been before; we are redefining automobile construction."

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The five-door hatchback i3 isn't all carbon fiber. An aluminum chassis carries the suspension, steering, and drivetrain. It's similar to General Motors' 2002 AUTOnomy fuel-cell concept. On top of that base sits the carbon-fiber passenger cell on which the plastic body panels hang.

To get the i3 into showrooms at an affordable price, BMW needed to drastically reduce the cost of that carbon-fiber cell. The production itself is a well-known process called resin-transfer molding (RTM), in which the carbon fibers are shaped into mats and placed in a two-piece mold before resin glue is injected at high pressure. After RTM, the rigid carbon panels are glued together as accurately as possible.

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BMW claims to have halved the production time from what it was a decade ago, partly by buying into the sourcing process with a joint venture with carbon specialists SGL Automotive Carbon Fibres to weave carbon thread into dry mats at its hydroelectric powered plant in Washington State. The mats contain a binder agent, and when they arrive at the Leipzig factory they are preformed using ultrasound to activate the binder agent and hold an approximate shape. Each body side uses nine panels.

Before the resin is added, most of the excess is trimmed. Normally these scraps would be useless, but BMW uses a special combing machine to align the scrap fibers so they can be reformed into a series of strong preformed panels, which are used to make the i3's non-load-bearing roof. For the main body sides, the preformed mats are placed into the RTM machine molds and injected with resin at 1160 psi and heated to 100 C to set. Each panel is then trimmed and cleaned, and the required holes are cut using water jets. Robots assemble the body using 525 feet per car of weatherproof and temperature-stable Dow Corning polyurethane glue.

Cleanliness is so vital that workers wear gloves—the sweat off a finger can ruin a glued joint. To prevent contamination of the panels, 160 robots in the assembly hall take care of the key assembly processes. It's slower than a classic stamped-steel car plant, but not by much, BMW says, and eliminating the press shop and the paint shop saves precious time. Using light and heat to set the panels saves even more.

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At a nearby plant BMW builds its 1-series at a rate of 700 to 750 a day. Uwe Taver, the i3's body-shop manager, admits that i3 production is some way off that. "But i3 bodies take just a few minutes to set," he says. "Compared to classic body construction, we are getting closer."

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There's less heavy machinery here than in a typical car plan. There are no conveyors, no welding, and the robots (aside from those that bond the body pieces) are lighter-duty, cheaper models because they don't have to carry too much weight. The body shop is relatively peaceful compared with a traditional steel-stamping plant. Paint is still involved, however, and while BMW claims that the i3 is the world's greenest car, the automaker is not clear whether that includes the way in which the 1-series plant sprays the car's plastic outer body panels.

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BMW claims that in the 100 or so crash tests it has performed, the i3's carbon-fiber construction is at least as safe as, if not safer than, a conventional car. During an impact, the main battery that's carried under the floor automatically disconnects using an explosive fuse, the residual system charge is drained, and the motor regeneration electronics are isolated. Carbon fiber is also cheaper to repair, according to BMW. What's more, BMW says that more than 95 percent of typical accidents will affect only the outer skin panels, which can be easily replaced, with just 2.5 percent affecting the aluminum rolling chassis and 2.5 percent the inner carbon-fiber body.

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If it is not exactly cheaper, the carbon-fiber construction is certainly lighter. The i3 weighs in at 2755 pounds, where a steel version would have weighed 3306 pounds, and an all-aluminum version 3141 pounds. We're talking about hundreds of pounds in savings, then, which BMW claims will give the i3 superior agility and range compared with heavier battery-powered rivals such as the Nissan Leaf (3450 pounds), Renault Fluence (3538 pounds) and other forthcoming battery electric cars from the likes of Ford.

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